• Advances in concrete construction
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• v.10 no.2
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• pp.171-183
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• 2020

The main objective of this study is the assessment of the ability of limestone mortars to resist to different chemical attacks. The ability of polypropylene (PP) fibres waste used as reinforcement of these concrete materials to enhance their durability is also studied. Crushed sand 0/2 mm which is a fine limestone residue obtained by the crushing of natural rocks in aggregates industry is used for the fabrication of the mortar. The fibres used, which are obtained from the waste of domestic plastic sweeps' fabrication, have a length of 20 mm and a diameter ranging between 0.38 and 0.51 mm. Two weight fibres contents are used, 0.5 and 1%. The durability tests carried out in this investigation included the water absorption by capillarity, the mass variation, the flexural and the compressive strengths of the mortar specimens immersed for 366 days in 5% sodium chloride, 5% magnesium sulphate and 5% sulphuric acid solutions. A mineralogical analysis by X-ray diffraction (XRD) and a visual inspection are used for a better examination of the quality of tested mortars and for better interpretation of their behaviour in different solutions. The results indicate that the reinforcement of limestone mortar by PP fibres waste is an excellent solution to improve its chemical resistance and durability. Moreover, the presence of PP fibres waste does not affect significantly the water absorption by capillarity of mortar nether its mass variation, when exposed to chloride and sulphate solutions. While in sulphuric acid, the mass loss is higher with the presence of PP fibres waste, especially after an exposure of 180 days. The results reveal that these fibres have a considerable effect of the flexural and the compressive behaviour of mortar especially in acid solution, where a reduction of strength loss is observed. The mineralogical analysis confirms the good behaviour of mortar immersed in sulphate and chloride solutions; and shows that more gypsum is formed in mortar exposed to acid environment causing its rapid degradation. The visual observation reveals that only samples exposed to acid attack during 366 days have showed a surface damage extending over a depth of approximately 300 ㎛.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.170-174
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• 2008

Recently, a problem related to the thermal management in portable electronic and telecommunication devices is becoming issued. That is due to the trend of slimness of the devices, so it is not easy to find the optimal thermal management technology for the devices. From now on, a pressed circular type cooling device has been mainly used, however the cooling device with thin thickness is becoming needed by the inner space constraint. In the present study, the silicon and metal flat plate type cooling device with the separated vapor and liquid flow path was designed and fabricated. Through the experimental study, the normal isothermal characteristic by vapor-liquid phase change was confirmed and the cooling device with 70mm of total length showed 6.8W of the heat transfer rate within the range of $4{\sim}5^{\circ}C$/W of thermal resistance. In the meantime, the metal cooling device was developed for commercialization. The device was designed to have all structures of evaporator, vapor flow path, liquid flow path and condenser in one plate. And an envelope of that could be completed by combining the two plates of same structure and size. And the simplicity of fabrication process and reduction of manufacturing cost could be accomplished by using the stamping technology for fabricating large flow paths relatively. In the future, it will be possible to develop the commercialized cooling device by revising the fabrication process and enhancing the thermal performance of that.

• Korean Journal of Plant Taxonomy
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• v.40 no.1
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• pp.50-58
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• 2010

The nutlet morphology and pericarp structure of 14 taxa (4 taxa of the genus Glechoma and related taxa) were studied by light and scanning electron microscopy, and a detailed description of nutlet morphological features for all examined taxa is provided. The shape of the nutlet is ovate to elliptic. Its size is 1.36-3.83 mm in length and 0.80-2.65 mm in width. The largest one was found in Marmoritis rotundifolia, while the smallest one was in Agastache nepetoides. Three different surface types were recognized in the studied taxa based on differences in cell outline and cell boundary relief (rectangular, pitted, and ridged negative reticulate-cell). Three types of trichome (uni-cellular non-glandular trichome, multi-cellular non-glandular trichome, and peltate glandular trichome) were distributed in the nutlets. The pericarp is formed in three layers (i.e., exocarp, mesocarp, and endocarp including sclenchyma tissue), and the pericarp in the studied species is $39.0-237.5{\mu}m$ thick. The morphological and anatomical features (the nutlet shape, surface type, and trichome distribution) in the genus Glechoma and related taxa are described and discussed.

• Food Science and Preservation
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• v.10 no.4
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• pp.527-533
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• 2003

This study was performed for increasing the consumption and developing the function of pumpkin(Cucurbita moschata DUCH.) seed. The changes of the contents of general chemical compositions, fatty acids, amino acids, ascorbic acid and ${\beta}$-carotene during sprouting were analyzed. Also, the bitter taste, which was produced during sprouting, were purified by using thin layer chromatography and preparative high pressure liquid chromatography. The purified bitter compound was identified by mass spectrum and nuclear magnetic resonance($^1$H '||'&'||' $\^$13/C-NMR). Weight of pumpkin seed sprout was increased to 348.4% and the length of stem was dramatically increased at 8 days. In each head and stem parts of the pumpkin seed sprout, the contents of protein and lipid were decreased, however, the contents of fiber, ash and soluble inorganic nitrogen were increased. The fatty acids of the pumpkin seed sprout were mainly represented as linoleic acid, oleic acid, palmitic acid and stearic acid. During sprouting, palmitic acid was gradually increased, reversely, linoleic acid was gradually decreased. The general amino acids of head part in the pumpkin seed sprout grown at 23$^{\circ}C$ during 8 days were orderly more contained glycine, alanine, arginine, cystein and proline. Those of free amino acids were orderly more contained arginine, threonine, alanine and glutamine. The contents of L-ascorbic acid and ${\beta}$-camtene of the pumpkin seed sprout were gradually increased with increasing sprouting days. The bitter taste material of head part of the pumpkin seed sprout was detected at Rf value 0.72 on silicagel TLC plate and separuted as one peak by HPLC. The chemical structure of the puified bitter compound was identified as a cucurbitacin glycoside by MS and NMR. The content of bitter compound at 8 days was contained 42.2 mg per 1kg sprout head.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.22 no.3
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• pp.319-329
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• 2000

Prediction of the soft tissue changes following hard tissue movement is very important from the esthetic view point for patients who have orthognathic surgery. There are many cephalometric analysis of facial bone and soft tissue on the lower lip and chin region but few soft tissue analysis on the midface after mandibular setback surgery. This study was performed to obtain whether the mandibular posterior movement has influence on the midface and the predictable ratio of post-operative measurement values of the soft tissue changes following mandibular setback surgery. Fifteen patients (8 males and 7 females) who had undergone mandibular setback surgery were selected and analyzed the soft tissue movement on the upper lip and the cheek region. Post-operative changes of the soft tissue measurements after mandibular surgery were examined on pre- and post-operative cephalometrics and the ratio of changes were analyzed after drawing the reference line on the face with the barium sulfate solution. The reference lines were perpendicular to the intercanthal line from infraorbital foramen and lateral canthus. The results obtained were as follows : 1. There were tendancy of anterior movement of soft tissue adjacent the nose after mandibular surgery 2. There were incerased tendancy of the amount of anterior movement from the nasal crease to the cheek region. 3. The amount of anterior movement of the soft tissue was larger below the palatal plane compared with above the palatal plane in the cheek region. 4. The upper lip length was increased and moved posterior direction after mandibular setback surgery 5. The lower lip was moved posterior direction by posterior movement of the mandibular structure 6. Soft tissue of the midface around the nose moved anterior direction after mandibular setback surgery but there was no correlation between the amount of mandibular setback and the amount of the soft tissue changes

• Maxillofacial Plastic and Reconstructive Surgery
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• v.40
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• pp.40.1-40.8
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• 2018

Background: A 9-year-old male showed severe defects in midface structures, which resulted in maxillary hypoplasia, ocular hypertelorism, relative mandibular prognathism, and syndactyly. He had been diagnosed as having Apert syndrome and received a surgery of frontal calvaria distraction osteotomy to treat the steep forehead at 6 months old, and a surgery of digital separation to treat severe syndactyly of both hands at 6 years old. Nevertheless, he still showed a turribrachycephalic cranial profile with proptosis, a horizontal groove above supraorbital ridge, and a short nose with bulbous tip. Methods: Fundamental aberrant growth may be associated with the cranial base structure in radiological observation. Results: The Apert syndrome patient had a shorter and thinner nasal septum in panthomogram, PA view, and Waters' view; shorter zygomatico-maxillary width (83.5 mm) in Waters' view; shorter length between the sella and nasion (63.7 mm) on cephalogram; and bigger zygomatic axis angle of the cranial base (118.2°) in basal cranial view than a normal 9-year-old male (94.8 mm, 72.5 mm, 98.1°, respectively). On the other hand, the Apert syndrome patient showed interdigitating calcification of coronal suture similar to that of a normal 30-year-old male in a skull PA view. Conclusion: Taken together, the Apert syndrome patient, 9 years old, showed retarded growth of the anterior cranial base affecting severe midface hypoplasia, which resulted in a hypoplastic nasal septum axis, retruded zygomatic axes, and retarded growth of the maxilla and palate even after frontal calvaria distraction osteotomy 8 years ago. Therefore, it was suggested that the severe midface hypoplasia and dysostotic facial profile of the present Apert syndrome case are closely relevant to the aberrant growth of the anterior cranial base supporting the whole oro-facial and forebrain development.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.5
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• pp.107-116
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• 2011

In this paper, a traffic adaptive sleep based medium access control (TAS-MAC) protocol for wireless sensor networks (WSNs) is proposed. The protocol aims for WSNs which consist of clustered sensor nodes and is based on TDMA-like schema. It is a typical schedule based mechanism which is adopted in previous protocols such as LEACH and Bit-Map Assisted MAC. The proposed MAC, however, considers unexpected long silent period in which sensor nodes have no data input and events do not happen in monitoring environment. With the simple traffic measurement, the TAS-MAC eliminates scheduling phases consuming energy in previous centralized approaches. A frame structure of the protocol includes three periods, investigation (I), transmission (T), and sleep-period (S). Through the I-period, TAS-MAC aggregates current traffic information from each end node and dynamically decide the length of sleep period to avoid energy waste in long silent period. In spite of the energy efficiency of this approach, the delay of data might increase. Thus, we propose an advanced version of TAS-MAC as well, each node in cluster sends one or more data packets to cluster head during the T-period of a frame. Through simulation, the performance in terms of energy consumption and transmission delay is evaluated. By comparing to BMA-MAC, the results indicate the proposed protocol is more energy efficient with tolerable expense in latency, especially in variable traffic situation.

• Journal of IKEEE
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• v.17 no.1
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• pp.71-76
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• 2013

AlGaN/GaN HEMTs (High electron mobility transistors) with narrow channel were fabricated and the effect of channel scaling on the device were investigated. The devices were fabricated using e-beam lithography to have same channel length of $1{\mu}m$ and various channel width from 0.5 to $9{\mu}m$. The sheet resistance of the channel was increased corresponding to the decrease of channel width and the increase was larger at the width of sub-${\mu}m$. The threshold voltage of the HEMT with $1.6{\mu}m$ and $9{\mu}m$ channel width was -2.85 V. The transistor showed a variation of 50 mV at the width of $0.9{\mu}m$ and the variation 350 mV at $0.5{\mu}m$. The transconductance of 250 mS/mm was decreased to 150 mS/mm corresponding to the decrease of channel width. Also, the gate leakage current of the HEMT decreased with channel width. But the degree of was reduced at the width of sub-${\mu}m$. It was thought that the variation of the electrical characteristics of the HEMT corresponding to the channel width came from the reduced Piezoelectric field of the AlGaN/GaN structure by the strain relief.

• Korean Journal of Ichthyology
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• v.19 no.3
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• pp.225-235
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• 2007

The freshwater fish fauna and physical characteristics of streams in Yeosu peninsula and Geumo Islands were surveyed at thirty nine stations in the period of 2003 and 2005. Most of the streams were short in length and narrow in flowing water width. Main materials of riverbed in most stations were cobble, pebble and gravel; those in the stations adjacent river mouth gravel and sand. In the river type, eighteen stations out of surveyed stations were upstream type: Aa. Thirty nine fish species belonging sixteen families were caught in this survey region. Among them twenty seven species were primary freshwater fishes and nine were peripheral. In the species composition of each family, there were the most species in Cyprinidae and Gobiidae, twelve and ten species, respectively. Endemic species of Korean peninsula in this region were eight species. One exotic fish species, Lepomis macrochirus was found in Yeosu peninsula. Dominant species in each district was Zacco temminckii in Yeosu peninsula, Rhinogobius brunneus in Dolsan Island, Leucopsarion petersii in Geumo island and Oryzias latipes in Gae island. In the analysis of community structure, it was appeared that the community of Yeosu peninsula was the most diverse and stable in this region; as the size of island became smaller, diversity and richness of community decreased. Kichulchoia brevifasciata did not caught in this survey, and it is possible that the species was extincted in this island. Acanthorhodeus gracilis and L. petersii were reported firstly in this region.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.5
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• pp.237-242
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• 2010

Magnesium-substituted BCP (biphasic calcium phosphate) powders were prepared by incorporating small amounts of magnesium into the structure of different hydroxyapatite (HAp)/${\beta}$-tricalcium phosphate (${\beta}$-TCP) ratios through coprecipitation method. A series of magnesium substitutions ranging from 0, 0.5, and 1.0 wt%, which are comparable to the measured magnesium contents, were performed. The obtained powders were characterized by the following analytical techniques: X-ray diffraction analysis (XRD), Thermo Gravimetric Analyzer (TGA) and Fourier transform infrared spectroscopy (FT-IR). The results have shown that substitution of magnesium in the calcium-deficient apatites resulted in the formation of biphasic mixtures of different HAP/${\beta}$-TCP ratios after heating above $1000^{\circ}C$. The 1.0 wt% magnesiumsubstituted-BCP were soaked in Hank's solutions after 2 weeks to observe the morphology of the biocement, especially needle-like hydroxyapatite crystals and to estimate the length and diameter of nanoneedle crystals.